John Edwards admitted to ABC News in an interview with Bob Woodruff Friday (WATCH THE INTERVIEW) that he repeatedly lied about an extramarital affair with a 42-year old campaign employee, but strenuously denied being involved in paying the woman hush money or fathering her newborn child. The former Democratic U.S. senator from North Carolina said he would be willing to take a paternity test and divulge the results publicly.

"Two years ago I made a very serious mistake, a mistake that I am responsible for and no one else. In 2006, I told Elizabeth about the mistake, asked her for her forgiveness, asked God for his forgiveness. And we have kept this within our family since that time."

Edwards, 55, said he told his entire family about the affair after it ended in 2006, and that his wife Elizabeth, who has incurable breast cancer, was "furious" but that their marriage would survive. The couple have three children, Cate, 25, Emma, 9, and Jack, 7.

When he confessed his affair to his wife, "she was mad," Edwards said.

"She was angry," he said. "I think 'furious' would be a good way to describe it. She didn't understand. We both went through a process of trying to figure out how it happened, why it happened."

Late Friday evening, Elizabeth Edwards posted a message on her blog, saying that she and her children will stand by Edwards.

John Edwards: Part 1

"Our family has been through a lot. Some caused by nature, some caused by human weakness, and some – most recently – caused by the desire for sensationalism and profit without any regard for the human consequences," she wrote on her blog. "None of these has been easy. But we have stood with one another through them all. Although John believes he should stand alone and take the consequences of his action now, when the door closes behind him, he has his family waiting for him."

She too, denied in the blog post that Hunter's child was fathered by her husband.

Edwards told ABC News that he met secretly with former lover Rielle Hunter as recently as last month in a California hotel room at her request because "she was having some trouble, she just wanted to talk."

John Edwards: Part 3

"I wanted her not to tell the public what had happened," he said at another point. "Very simple. That's the reason I went."

Edwards contacted ABC News and requested that he be interviewed about the allegations. He agreed before the interview to place no limitations on the questions he would be asked, but limited the amount of time he would be questioned. He declined to clarify exactly when the relationship began or ended but said it was over before he announced his campaign for the presidency on Dec. 28, 2006.

"I think my family is entitled to every detail," Edwards said. "They've been told every detail…I think beyond the basics…I think that's where it stops in terms of the public because I think everything else is within my family and those privacy boundaries out to be respected."